Support for steam generator drums



Aug. 11, 1953 L. J- MARSHALL SUPPORT FOR STEAM GENERATOR DRUMS 2 Sheets-Sheet 1 Filed Nov. 22, 1947 INVEN TOR.

Leonard J. Marshall L. J. MARSHALL SUPPORT FOR STEAM GENERATOR DRUMS Aug. 11, 1953 2 She'ets-Sheet 2 Filed Nov. 22, 1947 INVENTOR.

Leonard J. Marshall Patented Aug. 11 1953 2,648,316 SUPPORT FOR STEAM GENERATOR DRUMS Leonard J. Marshall, Oak Ridge, Tenn., assignor to Combustion Engineering, Inc., a corporation of Delaware Application November 22, 1947, Serial No. 787,500

3 Claims.

My invention relates to steam generators of the type wherein an upper steam and water drum spanning the fuel combustion chamber top has water wall tubes extending from the drum downwardly along opposing chamber sides and into side headers therebelow.

Broadly stated, the object of my invention is to provide improved means for supporting said upper drum in the position named through the the following description of an illustrative embodiment of the invention when taken in conjunction with the accompanying drawings where-- Fig. l is a sectional elevation on line [-4 of Fig. 2 of a steam boiler which incorporates the improvements of this invention;

Fig. 2 is a front view of the same boiler showing the left portion thereof in elevation and the right portion in section as taken on line 2-2 of Fig. 1;

Fig. 3 is an enlarged showing in elevation (as viewed from the interior of the Figs. 1-2 boiler) of the four upright tubes interbraced in accordance with this invention to provide a strong structural support for each end of the boilers upper drum;

Fig. 4 represents the same four tubes as viewed in side elevation from line 4-4 of Fig. 3;

Fig. 5 is a section on line 5--5 of Figs. 3-4 showing how these interbraced tubes define the four corners of a drum-supporting girder structure of high rigidity and enhanced load-carrying strength; and r Fig. 6 is a section on line 66 of earlier views showing certain further details.

The steam generator here shown as incorporating my inventive improvements is characterized by its simplicity of construction, high operating efiiciency, low cost of maintenance, and ease of accessibility to all portions of the unit. It comprises a setting formed by a front wall 8, a rear wall 9, side walls I0 and II and a roof l2. Within the setting are the pressure parts of the unit, a substantial portion of the steam generating surface being formed by banks of boiler tubes l3 extending between an upper steam and water drum l5 and a laterally displaced lower water drum [6.

As illustrated, the drums I5 and it are laterally offset a considerable distance, the lower drum l8 extending adjacent the units rear wall 9 and the upper drum [5 spanning the top of the front furnace or combustion chamber section of the unit. Support for the lower drum [6 may be provided in any suitable manner such as by use of conventional cradles I! (see Fig. 1) carried by the concrete foundation l8. A bank of superheater tubes l9 may if desired also be included in the unit, in which event the superheated steam may be taken from the generator via header [4.

Beneath the upper drum I5 is the boilers combustion chamber, here illustratively shown as being fired by oil or gas burners 20 mounted in the lower portion of front wall 8. Solid fuels such as coal may instead be burned, in which case a suitable grate (not shown) will be provided in the combustion chamber bottom along with spreader, underfeed or other stoker means (again not represented) for properly feeding the fuel to that grate.

Lining opposing sides of the combustion chamber interior are Water wall tubes 22, here represented as singe lines (as are boiler tubes [3 also). These several tubes 2 along either side of the unit extend downwardly from close to one end of upper drum IE to a bottom header 23 disposed along the combustion chamber side as indicated. Each of these two bottom headers 23 is shown as deriving its support from the concrete foundation l8 through an I beam 24 running underneath the header in the manner best shown by Fig. 2. Other equivalent expedients for bottom-supporting the headers 23 are of course useable.

In this illustrative boiler furnace, the hot combustion gases produced by the flames (not shown) from burners 20 rise upwardly through the combustion chamber, first heating the water in side wall tubes 22, and then passing through boiler tube banks [3, as guided by bafiles 26 and 21, where more heat is extracted to convert the boiler water into steam; the spent combustion gases then leave the setting by way of flue 28, which if desired may contain dampers 29 for adjusting the chimney draft; and the bottom headers 23 receive water from upper drum IS in part through a down-flow circuit shown as including tubes 2] and a header 25 along the furnace front.

In accordance with my invention, each end of the upper steam and water drum I5 is support- 3 ed on a header 23 therebeneath through a. rigid girder-like structure that includes the two central wall lining tubes 22a plus a pair of outer downcomer tubes 30 interbraced with each other and with the inner tubes 22a in the unique manner best represented by Figs. 3-4-5.

From Figs. 1-2 it will be seen that one pair of the tubes 22a extends along the inner surface of wall I l on the combustion chambers right; that a second pair of these tubes 22a similarly extends along the inner surface of wall In on the chambers left; and that each of these two inner tube 22a sets is supplemented by a pair of outer tubes 30 interbraced and otherwise correlated therewith as indicated.

Looking first at the inner tubes 22a, each of these may satisfactorily be of the same diameter and wall thickness as the other side wall tubes 22 (here shown single line to simplify the drawing) which line the combustion chamber wall In the illustrative boiler represented all of these tubes 22 and 22a have an outside diameter of 3 inches and a wall thickness of one-eighth inch The represented offsetting (see Figs. 1 and 3) of tubes 22a at their lower ends is to allow outer tubes 30 to enter the same header 23 along its top between the tubes 22a, as Figs. 1 to 4 indicate.

Looking next at the outer tubes 30, these satisfactorily may be of the same diameter as the inner tubes 22a but preferably their wall thickness is greater than that of those inner tubes. In the illustrative boiler shown each tube 30 has an outside diameter of 3 inches and a wall thickness of one-quarter inch (twice that of the inner tubes 22 and 22a). The represented offsetting of tubes at their lower ends (see Figs. 2 and 4) is occasioned by the indicated spacing of the main length of these outer tubes 36 from the inner tubes 22a to establish the four-cornered girder structure shown in Fig. 5. If desired the lower bent portion of each outer tube 30 may be provided with a base fitting organized as shown at 3| in Figs. 2 and 4.

In order to increase the rigidity of the fourtube girder structure mentioned above, each of outer tubes 33 thereof is interbraced with the other outer tube and also with the inner tube 22a that is closest thereto. In the illustrative arrangement disclosed such interbracing between the two tubes 30 is effected through lugs 32 (three sets represented) plus a stiffener plate 33 bolted (or riveted) thereto as indicated at 35 (see Figs. 3 and 5). Each of these lugs 32 is welded or otherwise secured to the side of tube 30 which it contacts, thereby establishing a firm mechanical connection of each tube 30 to the other tube 30. Other means for effecting an equivalent interbracing are of course useable.

The represented interbracing between each tube 30 and the inner tube 22a aligned therewith is generally similar to that which the preceding paragraph describes. Welded to each tube 22a are three lugs 37; welded to each tube 30 are three other lugs 38 staggered with lugs 31 as shown (Fig. 4) spanning all six lugs 31-38 in each set is a stiffener plate 40; and securing all of those lugs to that plate are bolts (or rivets) 4| disposed in a single row as shown by Figs. 4-5. Other means for effecting an equivalent interbracing of each tube 30 to its companion tube 22a are of course useable.

Inner tubes 22a are preferably not interbraced one to the other since to do so would expose the non-water-cooled bracing parts to the hightemperature heat of the combustion chamber interior; also a placing of such parts between the tubes would interfere with the refractory brick sections 43 (see Fig. 5) that desirably back and fill the inter-tube space in conventional manner. In the illustrative boiler furnace disclosed such bricks 43 of refractory material (although not fully represented) fully line (between tubes 22) each of the combustion chamber side walls In and II, and are not interfered with by the tube bracing expedients of the present invention.

The provision, moreover, of outer tubes 30 to complete the novel drum-supporting columns hereof likewise correlates conveniently with conventional constructions for generator side walls In and II as Figs. 1, 4 and 5 clearly show. As indicated by the simplified showing of Fig. 6, room for these outer tubes is present in the wall space immediately inside the metal outer casing sheet I 0 or I I (see Fig. 2) between it and the backs of refractory brick 43 (see Fig. 5). This space is conventionally packed with heat-insulating material (not shown) such as asbestos wool.

Each of the resultant drum-supporting tube assemblages 22a30 is characterized by high rigidity and a load-carrying capacity far in excess of the sum of the individual capacities of the four tubes (when unstiffened) which make up the assemblage. This added strength results from the interbracing expedients herein disclosed. In a steam generator having the simplified construction here illustrated such added strength bolsters the factor of safety with which the relatively heavy upper drum l5 can be supported through the medium of steam and water tubes that extend from the drum ends downwardly into the headers 23 beneath those ends.

A further advantage of the added outer tubes 30 is that they improve the Water circulation in the steam generator with which used. Through them water from the drum [5 flows downwardly (in supplement to that through front-wall tubes 2|) into the headers 23, from which it rises upwardly through tubes 22a. and 22 exposed to the combustion chamber heat. Since, moreover, these downcomers 30 are of heavier wall thickness than riser tubes 22a, a proportionately greater share of the total drum load is carried by them.

From the foregoing it will accordingly be seen that I have improved the construction of steam generators wherein an upper steam and water drum spans the fuel combustion chamber top and has water wall tubes extending from the drum downwardly into side headers disposed beneath the drum; that I have provided improved means for supporting said drum in the position named through the medium of steam and water tubes which extend upwardly from said headers and into the drum at points immediately above the headers; and that I have increased the rigidity and load-carrying capacity of such verticallydisposed steam and water tubes when employed as structural members to support the boiler drum in the manner aforesaid.

My inventive improvements are therefore capable of broad application and hence are not to be restricted to the specific form here disclosed by way of illustration.

What I claim is:

1. In a steam generator the combination of a furnace chamber which includes a side wall and which contains hot combustion gases; an upper steam and water drum crossing said side wall at the chamber top; a header extending along the side wall beneath the drum; bottom supporting means for the header; at least two inner upright steam and water riser tubes extending from the header substantially straight upwardly along the inner heated face of said side wall into said drum and absorbing heat from said furnace chamber by direct contact with said hot combustion gases; at least two outer upright water downcomer tubes extending downwardly from the drum in substantial alignment with said riser tubes but along the outer relatively cool portion of said side wall and thence into said header, said downcomer tubes being shielded from the heat of said furnace chamber by said side wall and being free of direct contact with said hot combustion gases; and means for mechanically interbracing each of said outer cool water downcomer tubes with one of said inner heated riser tubes and the two downcomer tubes with each other whereby to form those tubes into a steam and water cooled drum supporting column of high stiffness and enhanced load carrying capacity.

2. In a steam generator comprising a, furnace chamber defined in part by opposed side walls and containing hot combustion gases, an upper steam and water drum extending across the chamber top transversely over the side walls, a header for each side wall extending along the lower portion thereof and bottom-support means for each header, the combination of a self cooling water and steam circulating support assemblage comprising an inner pair of vertical steam and water riser tubes at each end of the drum extending therefrom substantially straight downwardly along the inner heated face of the side wall beneath that end and into the header for that side wall and being in direct contact with the said hot combustion gases, an outer pair of vertical downcomer water tubes at each drum end also extending downwardly therefrom in substantial alignment with said riser tubes but along the outer relatively cool portion of the said side wall at that end and thence into the header for that side wall, said downcomer water tubes being shielded from the heat of the furnace chamber by that portion of said side wall located between said downcomer tubes and said riser tubes and being free of direct contact with said hot combustion gases, and means in each of the aforesaid four-tube drum support assemblages for mechanically interbracing the two outer cool downcomer tubes thereof with each other and each with one of the inner heated riser tubes thereof whereby to increase the stiffness and load-carrying strength of the steam and water cooled assemblage.

3. In a steam generator the combination of an upper steam and water drum; a lower water conduit; bottom supporting means for said conduit; a furnace chamber including a side wall and containing hot combustion gases; at least one upright steam evaporating riser tube extending upwardly from said lower water conduit to said upper steam and water drum, said riser tube forming part of the inner heated face of said furnace side wall and absorbing heat from the furnace chamber by direct contact with said hot combustion gases; at least one outer upright water downcomer tube extending downwardly from said upper steam and water drum in substantial alignment with said riser tube but along the outer relatively cool portion of said wall and thence into said lower water conduit, said downcomer water tube being shielded from the heat of the furnace chamber by said side wall and being free of direct contact with said hot combustion gases; and means for mechanically interbracing said outer water tube with said inner heated tube, whereby to form those tubes into a water and steam cooled drum supporting column of high stiffness and enhanced load carrying capacity.

LEONARD J. MARSHALL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 597,151 Fall Jan. 11, 1898 1,745,485 Harter Feb. 4, 1930 2,133,979 Firshing Oct. 25, 1938 2,332,534 Rooney Oct. 26, 1943 2,413,149 McCarthy et a1. Dec. 24, 1946 2,570,073 Reintjes Oct. 2, 1951 FOREIGN PATENTS Number Country Date 310,695 Great Britain May 2, 1929 

